NCC 2022 Ventilation Requirements
What changed, what it means for new homes in South Australia, and how MVHR satisfies the code.
Who this is for: builders, designers, certifiers and homeowners working on new residential construction or significant renovations in South Australia. NCC 2022 Housing Provisions came into effect on 1 May 2023. All Class 1 building approvals lodged after this date are subject to the requirements below.
Why NCC 2022 changed ventilation requirements
Australian homes have become progressively more airtight over the past two decades. Better insulation, more careful construction practice, improved window sealing and draught-proofing have all reduced uncontrolled air leakage. This is good for energy efficiency and thermal comfort — but it creates a problem for indoor air quality.
In a leaky home, a certain volume of fresh air enters through gaps and cracks even when all windows are closed. This uncontrolled infiltration — while thermally inefficient — incidentally dilutes indoor moisture, CO₂ and pollutants. As homes have become tighter, this incidental dilution has reduced, and indoor air quality problems have increased.
NCC 2022 acknowledges this relationship explicitly for the first time: homes below a certain airtightness threshold must now have designed, installed mechanical ventilation. The code is formally recognising what building science has established for decades — tight homes need purposeful ventilation.
The key changes
Mechanical ventilation for homes under 5 ACH50
VentilationWhat it requires
Where a dwelling has — or is designed to have — an air leakage rate of less than 5 ACH50, a mechanical ventilation system must be installed that provides at least the minimum calculated airflow rate.
The formula
Minimum Airflow (L/s) = 0.05 × Floor Area (m²) + 3.5 × (Number of Bedrooms + 1)
What this means in practice
A tighter building needs designed ventilation. The code formalises what building science has always required: if you reduce uncontrolled air leakage, you must replace it with controlled, purposeful ventilation. For most high-performance homes, this means MVHR.
Example calculation
A 220 m² four-bedroom home: 0.05 × 220 + 3.5 × 5 = 11 + 17.5 = 28.5 L/s minimum. A well-designed MVHR system for this home would typically be specified at 30–40 L/s to allow appropriate balancing and commissioning tolerance.
Exhaust systems — condensation management
Exhaust / CondensationDirect outdoor discharge required
Exhaust fans in kitchens, bathrooms, sanitary compartments and laundries must discharge directly to outdoor air via a duct or shaft. Venting into a roof cavity, sub-floor or wall cavity is explicitly non-compliant. This rule closes one of the most widespread and damaging installation errors in Australian residential construction.
Light switch interlock with 10-minute run-on
For bathrooms and sanitary compartments that do not have natural ventilation (i.e. no operable window or opening to outside), the exhaust fan must be wired to the light switch. It must turn on when the light is switched on, and continue running for a minimum of 10 minutes after the light is turned off. This ensures adequate post-shower extraction.
Why this matters
Inadequate bathroom exhaust is the single most common source of moisture damage in residential buildings. Ducting into a roof cavity — even with the best intentions — creates a long-term condensation and mould problem that is expensive to remediate and is typically not covered by building warranty.
External walls — vapour permeance
CondensationClimate zone-specific requirements
NCC 2022 introduced requirements for wall sarking vapour permeance classified to climate zone. South Australia spans climate zones 3 (hot dry) and 5 (warm temperate), with the Adelaide Hills at the boundary. Membranes in zones 4 and 5 must be Class 3 minimum vapour permeance.
Purpose
Moisture drive through wall assemblies varies significantly by climate. In temperate and cool climates, moisture can condense within the wall cavity — on the inside face of sarking or within insulation. Appropriate vapour control management reduces this risk, particularly in airtight, well-insulated homes where wall cavity temperatures may differ significantly from indoor conditions.
What counts as “under 5 ACH50”?
5 ACH50 (air changes per hour at 50 Pascals reference pressure) is the threshold at which Part 10.6.3 applies. To put this in context:
The average new home built today in South Australia is likely to sit between 5 and 12 ACH50 without deliberate airtightness work. Homes built with attention to airtightness — particularly those targeting high-performance or Passive House standards — will typically be below 3 ACH50 and are clearly within scope of the mechanical ventilation requirement.
Does NCC 2022 require blower door testing?
Not universally — but the picture is changing. Currently, the NCC 2022 mechanical ventilation requirement under Part 10.6.3 applies to homes that are tested and found to be below 5 ACH50. A builder or designer can also choose to design a home to be above 5 ACH50 and avoid the ventilation requirement — but in practice, modern construction is pushing homes toward tighter envelopes regardless.
NCC 2025 is expected to extend minimum airtightness performance requirements more broadly across the housing stock. The direction of travel is clear: tighter buildings, better-ventilated buildings.
Many builders and designers in South Australia are already specifying blower door tests proactively — to confirm compliance, de-risk defects claims, and demonstrate performance to clients. HiPer Haus provides blower door testing services across Adelaide and South Australia with full written reporting.
How MVHR satisfies NCC 2022
A properly designed and commissioned MVHR system is the most complete way to satisfy the NCC 2022 ventilation and condensation management requirements simultaneously:
Part 10.6.3 — minimum airflow
MVHR is designed to deliver at least the calculated minimum airflow rate to the dwelling, typically with a margin for balancing and commissioning.
Part 10.8.2 — direct outdoor discharge
MVHR extract terminals in bathrooms and kitchens duct directly to the outside via the central unit. No roof cavity venting.
Part 10.8.2 — continuous extraction
MVHR runs 24 hours a day at a set flow rate, ensuring bathrooms are continuously in negative pressure relative to living spaces — far exceeding the intermittent extraction of a standalone fan.
CO₂ and IAQ
Supply terminals in bedrooms and living areas deliver continuous fresh, filtered outdoor air — preventing the CO₂ accumulation that the code does not yet explicitly address but that affects occupant health and sleep.
Frequently asked questions
What did NCC 2022 change for ventilation in homes?
NCC 2022 introduced two significant changes relevant to ventilation. First, under Part 10.6.3, homes with airtightness below 5 ACH50 must now have mechanical ventilation meeting a minimum calculated airflow rate — formally recognising that modern tight construction requires designed ventilation. Second, under Part 10.8.2 (condensation management), bathroom and kitchen exhaust fans must discharge directly outside, and bathroom fans in rooms without natural ventilation must be interlocked with the light switch and continue running for 10 minutes after the light is turned off.
What is the NCC 2022 mechanical ventilation formula?
The minimum required airflow for a dwelling is calculated as: Airflow (L/s) = 0.05 × Floor Area (m²) + 3.5 × (Number of Bedrooms + 1). For example, a 200 m² four-bedroom home requires a minimum of 0.05 × 200 + 3.5 × 5 = 10 + 17.5 = 27.5 L/s of mechanical ventilation.
Does NCC 2022 require airtightness testing?
NCC 2022 does not mandate airtightness testing for all homes — the ventilation requirement under Part 10.6.3 applies to homes that are tested and found to be below 5 ACH50. However, NCC 2025 is expected to extend minimum airtightness requirements more broadly. Some states and many Passive House and high-performance projects already require blower door testing. Builders and designers in South Australia are increasingly specifying tests proactively to confirm compliance and performance.
Does MVHR satisfy NCC 2022 ventilation requirements?
Yes. A properly designed and commissioned MVHR system, providing the minimum calculated airflow rate to the dwelling, satisfies the mechanical ventilation requirement under NCC 2022 Part 10.6.3. MVHR also satisfies the exhaust requirements under Part 10.8.2 — extract terminals in bathrooms and kitchens discharge outside continuously, with a correctly specified system providing airflow at all times.
When did NCC 2022 come into effect in South Australia?
NCC 2022 was adopted nationally with the Housing Provisions standard coming into effect from 1 May 2023. South Australia adopted NCC 2022 on this date. All Class 1 buildings (new homes and additions) submitted for building approval after this date are subject to NCC 2022 requirements, including the ventilation and condensation management provisions.
Working on a project in South Australia?
HiPer Haus provides MVHR design, installation and commissioning for new homes and renovations across Adelaide and SA — including blower door testing for NCC compliance and Passive House certification.